The present invention generally relates to a conveyor frame assembly for use with a plastic chain conveyor belt. More specifically, the present invention relates to a conveyor assembly that reduces the catenary sag of the lower run of the conveyor belt downstream from the drive roller.
In many conveyor applications, a plastic chain conveyor belt is utilized to move materials throughout a facility. The plastic chain conveyor belt includes individual links that run across the width of the conveyor belt such that the conveyor belt can assume a flat transporting condition yet can transition over both a drive roller and an idler roller to create the upper and lower runs of the conveyor belt.
Since plastic chain conveyor belts can be used to move a large number of products throughout a facility, the weight of the products on the plastic belt and the wear of the belt links cause the belt to “stretch” when the belt is under load. When the belt is placed under a larger load, the “stretching” of the conveyor belt increases the length of the belt, which creates a sag in the lower run of the conveyor belt following the drive roller. This “loop” of chain hangs down immediately following the drive sprockets and is referred to as catenary sag. Since there is nearly zero tension on the chain immediately following the drive sprockets, the lower run of the conveyor belt sags beneath the lowermost edge of the spaced side rails of the conveyor assembly to create the catenary sag.
During conveyor design, the amount of catenary sag is calculated and the conveyor is designed to incorporate the catenary sag. Although the catenary sag allows the conveyor to compensate for the stretching of the conveyor belt under tension, the catenary sag oftentimes extends beneath the lower edge of the conveyor frame assembly. This causes many problems, including allowing the conveyor belt to be contacted by personnel in the area surrounding the conveyor frame assembly and greatly expanding the overall height of the conveyor.
Therefore, a need exists for a conveyor frame assembly that addresses the problems created by the catenary sag beneath the lower edge of the conveyor frame assembly. Further, a need exists for a conveyor assembly that allows for the stretching of the plastic belt while still addressing the cantenary sag of the lower run of the conveyor belt.